Saturday, January 6, 2018

JMeter―Select on Multiple Criteria with JSONPath

If your web services are RESTful, you will get JSON responses.  In Apache JMeter, there is a JSON Extractor (i.e., a Post Processor) available for parsing JSON responses.

In this article, we will introduce JSONPath, which is used in JSON Extractor, and present an example of selecting an object/element based on multiple criteria with it.[1]

JSON Extractor / JSONPath


One of the advantages of XML is the availability of numerous tools to analyse, transform and selectively extract data out of XML documents. XPath is one of these powerful tools.  For JSON, we have a similar tool called JSONPath.

JSONPath is the XPath for JSON.  Since a JSON structure is normally anonymous, JSONPath assigns symbol $ as the root object.

Below is a side-by-side comparison of the JSONPath syntax elements with its XPath counterparts.[3]


XPath
JSONPath
Description
/
$
the root object/element
.
@
the current object/element
/
. or []
child operator
..
n/a
parent operator
//
..
recursive descent. JSONPath borrows this syntax from E4X.
*
*
wildcard. All objects/elements regardless their names.
@
n/a
attribute access. JSON structures don't have attributes.
[]
[]
subscript operator. XPath uses it to iterate over element collections and for predicates. In Javascript and JSON it is the native array operator.
|
[,]
Union operator in XPath results in a combination of node sets. JSONPath allows alternate names or array indices as a set.
n/a
[start:end:step]
array slice operator borrowed from ES4.
[]
?()
applies a filter (script) expression.
n/a
()
script expression, using the underlying script engine.
()
n/a
grouping in Xpath

JSONPath expressions can use the dot–notation
$.ccapiInfo.canonicalLink

or the bracket–notation
$['ccapiInfo']['canonicalLink']

for input paths. For the internal or output paths, they will always be converted to the more general bracket–notation.  

Selecting on Multiple Criteria with JSONPath 


Given an array of books, the following JSONPath applies two filters (e.g., "price" and "category") on the array to retrieve the name of author matching the criteria:


JSON Input

{
    "store": {
        "book": [
            {
                "category": "reference",
                "author": "Nigel Rees",
                "title": "Sayings of the Century",
                "price": 8.95
            },
            {
                "category": "fiction",
                "author": "Evelyn Waugh",
                "title": "Sword of Honour",
                "price": 12.99
            },
            {
                "category": "fiction",
                "author": "Herman Melville",
                "title": "Moby Dick",
                "isbn": "0-553-21311-3",
                "price": 8.99
            },
            {
                "category": "fiction",
                "author": "J. R. R. Tolkien",
                "title": "The Lord of the Rings",
                "isbn": "0-395-19395-8",
                "price": 22.99
            }
        ],
        "bicycle": {
            "color": "red",
            "price": 19.95
        }
    },
    "expensive": 10
}

JSONPath Syntax


$..book[?(@.price==8.99 && @.category=='fiction')] .author


Below shows the evaluation result using JSONPath Online Evaluator with the above input and JSONPath Expression:


Evaluation Results

[
  "Herman Melville"
]


More Examples


Given the same input, you can also retrieve different objects (or elements) using the following JSONPath expressions:[4]

JSONPath expressions
Result
$.store.book[*].author
the authors of all books in the store
$..author
all authors
$.store.*
all things in store (four books, a blue ball)
$.store..price
the price of everything in the store
$..book[-1:]
the last book in order
$..book[0,1]
the first two books
$..*
all members of the JSON structure

References

  1. JsonPath AND Operator on Array
  2. JSONPath Online Evaluator - jsonpath.com
  3. JSONPath - XPath for JSON - stefan.goessner
  4. JSONPath reference
  5. JMeter: How to Verify JSON Response? (Xml and More)

Friday, January 5, 2018

JMeter―How to Use Firefox to Record Test Scenarios



This article will cover the details of recording HTTP/HTTPS traffic with Firefox (FF) in Apache JMeter. To achieve that, you can use a workbench with HTTP(S) Test Script Recorder.  If you are new to JMeter, watch the above video first.




"Recording" Template


The easiest way to create a complete Test Plan with the HTTP(S) Test Script Recorder is using Recording Template:[1]
  1. Go to JMETER_HOME/bin and start JMeter
  2. Select Templates... on the menu bar
  3. Select Recording template on the list
  4. A complete Test Plan is generated (see the diagram below)
Using "Recording" template, save you a lot of efforts.  For comparison, you can read [2] for manual steps.

In the HTTP Request Defaults element, you can optionally set "Server name":
Server name
enter example.com
Path
leave blank



JMeter Temporary Root CA


Return to HTTP(S) Test Script Recorder, and click the Start button at the top.
Note that you need to "Configure your browser to use the JMeter Proxy" (see the section below) first.  For the discussion only, we will show you the "JMeter Temporary Root CA" first.

This will start the JMeter proxy server which is used to intercept the browser requests. A file called ApacheJMeterTemporaryRootCA.crt will be generated in jmeter/bin folder and you will find a prompt showing below messages:



Installing the certificate in Firefox for HTTPS Recording


 If you're recording SSL/TLS traffic (i.e., your site URL has https prefix), you need to install the certificate (i.e., ApacheJMeterTemporaryRootCA.crt) in your browser. So, JMeter could record encrypted traffic.  If you don't know how to do it, read Installing the JMeter CA certificate for HTTPS recording first.

For the Firefox (or FF) browser, you choose the following options (note that the configuration looks different in different FF versions):
  • Tools / Options
  • Advanced / Certificates
  • View Certificates
  • Authorities
  • Import …
  • Browse to the JMeter launch directory, and click on the file ApacheJMeterTemporaryRootCA.crt, pressOpen
  • Click View<
    and check that the certificate details agree with the ones displayed by the JMeter Test Script Recorder
  • If OK, select "Trust this CA to identify web sites", and press OK
  • Close dialog by pressing OK as necessary 
After import, you can find a new entry on the Authorities list as shown below:



Configure Your Browser to Use the JMeter Proxy


Like many other web testing tools, JMeter records tests by inserting itself as an HTTP proxy between the browser and the web site.  We use FF as our browser when using the JMeter HTTP(S) Test Script Recorder because, unlike Chrome and some other browsers, it does allows you to override system-wide configuration for its proxy settings (see also [8]).

Configure Firefox to use localhost (127.0.0.1) on port 8080 (Note that you also need to set the Port to  be 8080 in HTTP(S) Test Script Recorder) as its proxy for all traffic by following these steps:[7]
  1. Open Firefox
  2. Go to the Preferences menu
    • From the tool bar, click Edit → Preferences (or Tools → Preferences or type about:preferences#advanced as URL). This should bring up the options.
  3. Click on the Advanced tab
  4. Then Network tab
  5. In the "Connection" section, click on "Settings..."
  6. Select the "Manual proxy configuration" radio button
  7. Set HTTP Proxy to "localhost" and Port to "8080"
  8. Check "Use this proxy server for all protocols"
  9. Click OK and exit the Preferences menu

Note: When Firefox is configured to use JMeter's Script Recorder as a proxy, it will only work properly if the Script Recorder is running.


Recording Tips


When you record, you may want to consider the following extra configurations:
  • Follow Redirects vs Redirect Automatically[3,4]
  • Retrieve All Embedded Resources from HTML Files
    • Set in HTTP Request sampler
    • Tell JMeter to parse the HTML file and send HTTP/HTTPS requests for all images, Java applets, JavaScript files, CSSs, etc. referenced in the file.
  • Firefox Data Collection and Use
  • Use the Transaction Controller[5]
    • To generate a “virtual” sample representing a real page to measure aggregate times of all nested samples (i.e., embedded resources―images, styles, scripts, recordings or anything that seems like a separate request).
    • Transaction controllers also provide scopes for JMeter test elements[10,11]
  • URL Patterns to Exclude
    • Set in HTTP(S) Test Script Recorder→ Requests Filtering
    • If the following patterns were not excluded yet, set them manually:
      • (?i).*\.(bmp|css|js|gif|ico|jpe?g|png|swf|woff|woff2)
      • (?i).*\.(bmp|css|js|gif|ico|jpe?g|png|swf|woff|woff2)[\?;].*
  • Post-recording updates of Test Scenarios
  • Prepare your click stream before recording
  • Use timers to simulate a virtual user’s “think time”

References

  1. Apache JMeter HTTP(S) Test Script Recorder (Apache Software Foundation)
  2. Apache JMeter HTTP(S) Test Script Recorder (pdf)
  3. When to use “Follow Redirects” & “Redirect Automatically” while recording with jmeter
  4. Difference Between Redirect Automatically and Follow Redirects in JMeter
  5. JMeter―Using the Transaction Controller (Xml and More)
  6. JMeter Proxy exclusion patterns still being recorded
  7. How To Use JMeter To Record Test Scenarios
  8. Use the Profile Manager to create and remove Firefox profiles (Mozilla)
  9. A Comprehensive Guide to Using JMeter Timers
  10. JMeter Scoping Rules - The Ultimate Guide
  11. Scope and Execution Order of Elements in Jmeter
  12. JMeter Beginner Tutorial 21 - How to use Test Script Recorder (video)